Chamber for Wafer Cleaning and Method for Making the Same

ABSTRACT

A wafer processing chamber “chamber” is provided. Broadly speaking, the chamber allows a fluid flow and a fluid pressure within the chamber to be controlled in a variable manner. More specifically, the chamber utilizes removable plates that can be configured to control the fluid flow and the fluid pressure in an inner volume within the chamber. Also, the removable plates can be used to separate the inner volume within the chamber from an outer volume within the chamber. In this manner, the removable plates can be used to create a pressure differential between the inner volume within the chamber and the outer volume within the chamber. A lower pressure in the outer volume within the chamber requires less outer chamber strength to withstand the lower pressure. A lower outer chamber strength requirement translates into an overall decrease in chamber size.

CLAIM OF PRIORITY

This application is a divisional application of U.S. patent applicationSer. No. 10/404,472, filed on Mar. 31, 2003, the disclosure of which isincorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to semiconductor waferprocessing. More specifically, the present invention relates to anapparatus in which a semiconductor wafer can be cleaned.

2. Description of the Related Art

In the manufacture of semiconductor devices, a surface of asemiconductor wafer (“wafer” or “substrate”) must be cleaned to removechemical and particulate contamination. If the contamination is notremoved, semiconductor devices on the wafer may perform poorly or becomedefective. Particulate contamination generally consists of tiny bits ofdistinctly defined material having an affinity to adhere to the surfaceof the wafer. Examples of particulate contamination can include organicand inorganic residues, such as silicon dust, silica, slurry residue,polymeric residue, metal flakes, atmospheric dust, plastic particles,and silicate particles, among others.

Wafer cleaning processes are generally performed by applying a fluid tothe surface of the wafer. In some instances the fluid is applied to thewafer in a sealed chamber. The method of applying the fluid to the wafercan influence the effectiveness of the wafer cleaning process. Forexample, a specific fluid flow pattern over the surface of the wafer mayprovide beneficial cleaning results. Additionally, a specific fluidpressure applied over the surface of the wafer may provide beneficialcleaning results. Traditionally, different wafer cleaning chambers havebeen required to obtain different fluid flow patterns and fluidpressures over the surface of the wafer. The need to have a differentwafer cleaning chambers to satisfy the requirements of a variety ofwafer cleaning processes can present problems with respect to overallwafer processing cost and implementation. Also, wafer cleaning processesthat require the use of high fluid pressures generally require the useof large wafer cleaning chambers to withstand the high pressure. Largerwafer cleaning chambers correspond to increased overall wafer processingcost.

In view of the foregoing, there is a need for a wafer cleaning chamberthat allows for variable control of fluid pressures and fluid flowpatterns as required to meet the needs of different wafer cleaningprocesses. The wafer cleaning chamber should also be able to accommodatewafers of different sizes. Furthermore, the wafer cleaning chambershould combine an ability to contain high pressures with an overallminimum size.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention provides a wafer processingchamber “chamber” that allows a fluid flow and a fluid pressure withinthe chamber to be controlled in a variable manner. More specifically,the chamber of the present invention utilizes removable plates that canbe configured to control the fluid flow and the fluid pressure in aninner volume within the chamber. Also, the removable plates can be usedto separate the inner volume within the chamber from an outer volumewithin the chamber. In this manner, the removable plates can be used tocreate a pressure differential between the inner volume within thechamber and the outer volume within the chamber. A lower pressure in theouter volume within the chamber requires less outer chamber strength towithstand the lower pressure. A lower outer chamber strength requirementtranslates into an overall decrease in chamber size. It should beappreciated that the present invention can be implemented in numerousways, including as a process, an apparatus, a system, a device, or amethod. Several embodiments of the present invention are describedbelow.

In one embodiment, a wafer cleaning chamber is disclosed. The wafercleaning chamber includes a lower support having a number of supportsurfaces. The lower support contains a first volume that exists betweenthe number of support surfaces. The wafer cleaning chamber furtherincludes a plate supported by the number of support surfaces of thelower support. The plate overlies the first volume in the lower support.The plate also has a number of wafer support surfaces to receive andsupport a wafer. A second volume exists between the number of wafersupport surfaces of the plate. Additionally, inlets and outlets arelocated in a periphery of the plate for introducing a fluid flow. Theinlets and outlets are positioned outside a location intended to receivethe wafer. The wafer cleaning chamber also includes an upper supportoverlying the plate. The upper support interfaces with the lower supportat a location outside the periphery of the plate. A third volume withinthe upper support overlies the wafer to be supported by the plate. Thethird volume is capable of accommodating a fluid flow. The fluid flowcan be introduced in a set configuration by the inlets and outlets ofthe plate. Also, the third volume is in limited fluid communication withthe first volume and the second volume.

In another embodiment, a wafer processing apparatus is disclosed. Thewafer processing apparatus includes a chamber having an upper portionand a lower portion. Support structures are distributed within a firstvolume that is defined in the lower portion of the chamber. Also,additional support structures are distributed within a second volumethat is defined within the upper portion of the chamber. The waferprocessing apparatus further includes a lower plate that is configuredto be disposed on the support structures of the lower portion of thechamber. When disposed on the support structures, the lower plateoverlies the first volume within the lower portion of the chamber. Thelower plate includes a number of wafer support structures distributedwithin a third volume defined within the lower plate. The number ofwafer support structures are capable of supporting a wafer. When thewafer is placed on the wafer support structures, the wafer overlies thethird volume within the lower plate. The wafer processing apparatus alsoincludes an upper plate configured to be attached to the supportstructures of the upper portion of the chamber. When the upper plate isattached to the support structures, the upper plate underlies the secondvolume defined within the upper portion of the chamber. The upper plateserves as an upper boundary of a fourth volume that exists between theupper plate and the wafer to be supported by the lower plate. The fourthvolume is capable of containing a fluid. Also, the fourth volume is inlimited fluid communication with the first volume, the second volume,and the third volume.

In another embodiment, a method for making a wafer processing chamber isdisclosed. The method includes forming a lower support plate that hassupport surfaces distributed within a first volume that is definedwithin the lower support plate. The first volume is defined to have afirst fluid inlet and a first fluid outlet. The method also includesforming a wafer support plate having wafer support surfaces distributedwithin a second volume that is defined within the wafer support plate.The wafer support surfaces are configured to receive a wafer. Oncereceived, the wafer forms an upper boundary for the second volumedefined within the wafer support plate. The second volume is defined tohave a second fluid inlet and a second fluid outlet. Additionally, fluidinlets and fluid outlets are provided at a periphery of the wafersupport plate and outside a location that is to receive the wafer. Themethod further includes securing the wafer support plate to the lowersupport plate. Once secured, the wafer support plate is supported by thesupport surfaces distributed within the first volume of the lowersupport plate. Also, the wafer support plate serves as an upper boundaryfor the first volume defined within the lower support plate. The methodcontinues with the forming of an upper support plate that contains athird volume configured to overlie the wafer to be received by the wafersupport surfaces of the wafer support plate. The method also includessecuring the upper support plate to the lower support plate to isolatethe third volume defined within the upper support plate from an outsideenvironment. The isolation of the third volume from the outsideenvironment is enabled by a seal disposed between the upper supportplate and the lower support plate.

In another embodiment, a method for performing a wafer cleaning processis disclosed. The method includes providing a chamber in which the wafercleaning process can be performed. The chamber includes a first volumeconfigured to overlie a wafer to be cleaned. The chamber also includes aplate configured to support the wafer. A second volume is defined withinthe plate directly below the wafer. The plate includes fluid inlets andfluid outlets defined in a periphery of the plate and outside a portionof the plate defined to support the wafer. The fluid inlets and fluidoutlets are oriented to direct a fluid flow through the first volume ina set pattern. Also in the chamber, a support structure is provided tosupport the plate. The support structure includes a third volume locateddirectly below the plate. The method includes an operation for placing awafer on the portion of the plate defined to support the wafer. Themethod further includes pressurizing the first volume to have a higherpressure than the second volume. The method also includes pressurizingthe second volume to have a higher pressure than the third volume. Thethird volume is pressurized to have a pressure between that of thesecond volume and an environment outside the chamber. Also in themethod, a fluid is provided to the first volume through the fluid inletsand is removed from the first volume through the fluid outlets, suchthat the fluid flows through the first volume in the set pattern. Thefluid is formulated to effect the wafer cleaning process.

In another embodiment, a method is disclosed for cleaning a wafer. Themethod includes an operation for placing a wafer on a support plate. Thesupport plate includes a number of fluid inlets and a number of fluidoutlets defined in a periphery of the support plate. The periphery ofthe support plate is defined outside an area of the support plate onwhich the wafer is placed. The method also includes an operation forflowing a cleaning fluid over the wafer from the number of fluid inletsto the number of fluid outlets in a set fluid flow pattern. The setfluid flow pattern is defined by positions and orientations of thenumber of fluid inlets and the number of fluid outlets.

Other aspects and advantages of the invention will become more apparentfrom the following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 is an illustration showing a vertical cross-section of a waferprocessing chamber (“chamber”), in accordance with one embodiment of thepresent invention;

FIG. 2 is an illustration showing a close-up view of a central portionof the chamber as shown in FIG. 1, in accordance with one embodiment ofthe present invention;

FIG. 3 is an illustration showing a top view of the lower plateconfigured to provide a linear fluid flow across the wafer, inaccordance with one embodiment of the present invention;

FIG. 4 is an illustration showing a top view of the lower plateconfigured to provide a conical fluid flow across the wafer, inaccordance with one embodiment of the present invention;

FIG. 5 is an illustration showing a top view of the lower plateconfigured to provide a spiral fluid flow across the wafer, inaccordance with one embodiment of the present invention;

FIG. 6 is an illustration showing a vertical cross-section of thechamber incorporating an upper plate, in accordance with one embodimentof the present invention;

FIG. 7 is an illustration showing a close-up view of a central portionof the chamber as shown in FIG. 6, in accordance with one embodiment ofthe present invention;

FIG. 8A is an illustration showing an upper plate configured to providea central fluid feed and a peripheral fluid exhaust, in accordance withone embodiment of the present invention;

FIG. 8B is an illustration showing the use of fluid channels within theupper plate, in accordance with one embodiment of the present invention;

FIG. 9 is an illustration showing an upper plate configured to provide aperipheral fluid feed and a central fluid exhaust, in accordance withone embodiment of the present invention;

FIG. 10 is an illustration showing an exemplary distribution of theinlets/outlets across the upper plate, in accordance with one embodimentof the present invention;

FIG. 11 is an illustration showing a flowchart of a method for making awafer processing chamber, in accordance with one embodiment of thepresent invention;

FIG. 12 is an illustration showing a flowchart of a method forperforming a wafer cleaning process, in accordance with one embodimentof the present invention; and

FIG. 13 is an illustration showing a generalized material phase diagram.

DETAILED DESCRIPTION

An invention is disclosed for a wafer processing chamber “chamber” and amethod for making the chamber. Broadly speaking, the present inventionprovides a chamber that allows a fluid flow and a fluid pressure withinthe chamber to be controlled in a variable manner. More specifically,the chamber of the present invention utilizes removable plates that canbe configured to control the fluid flow and the fluid pressure in aninner volume within the chamber. Also, the removable plates can be usedto separate the inner volume within the chamber from an outer volumewithin the chamber. In this manner, the removable plates can be used tocreate a pressure differential between the inner volume within thechamber and the outer volume within the chamber. A lower pressure in theouter volume within the chamber requires less outer chamber strength towithstand the lower pressure. A lower outer chamber strength requirementtranslates into an overall decrease in chamber size.

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail in order not to unnecessarily obscure the presentinvention.

FIG. 1 is an illustration showing a vertical cross-section of a waferprocessing chamber (“chamber”) 100, in accordance with one embodiment ofthe present invention. In one embodiment, the chamber 100 can serve as awafer cleaning chamber. The chamber 100 includes a lower support plate101 having a number of support surfaces 102. The support surfaces 102are distributed within an intermediate volume 113 defined within a topportion of the lower support plate 101. The support surfaces 102 arecapable of supporting a lower plate 109 at discrete locations in asubstantially uniform manner. The number and location of the supportsurfaces 102 depends on a pressure differential between the two sides ofthe lower plate 109. When placed on the support surfaces 102, the lowerplate 109 serves as an upper boundary to the intermediate volume 113.

The lower plate 109 can be secured to the lower support plate 101 by anumber of bolts 111. The lower plate 109 includes a number of wafersupport surfaces 110 distributed to provide substantially uniformsupport to a wafer 117 to be disposed within the chamber 100. The lowerplate 109 can be sized to allow the chamber 100 to process wafers ofdifferent sizes (e.g., 200 mm diameter, 300 mm diameter, etc. . . . ).The wafer support surfaces 110 are separated to form a lower volume 115.The lower volume 115 is located beneath the wafer 117 to be disposed onthe lower plate 109. Hence, with respect to the wafer 117, the lowervolume 115 is also referred to as an underlying volume 115.

The chamber 100 also includes an upper support plate 103 that isconfigured to interface with a top section of the lower support plate101. The upper support plate 103 includes a wafer processing volume 119.The wafer processing volume 119 is configured to overlie the wafer 117when the upper support plate 103 is attached to the lower support plate101. When the wafer 117 is present in the chamber 100, the top surfaceof the wafer 117 is exposed to the wafer processing volume 119. Hence,with respect to the wafer 117, the wafer processing volume 119 is alsoreferred to as an overlying volume 119.

A seal 107 is disposed between the upper support plate 103 and the lowersupport plate 101 at a peripheral location where the upper support plate103 and the lower support plate 101 are in contact. The seal 107traverses the periphery of the wafer processing volume 119 and serves toisolate the wafer processing volume 119 from an outside environment. Toenable the seal 107, the upper support plate 103 and lower support plate101 are forced together by a number of bolts 105 located outside aperiphery of the seal 107. Some wafer processes must be performed atextremely high pressures. Thus, the upper support plate 103, the lowersupport plate 101, and the bolts 105 provide sufficient strength towithstand a pressure which may exist within the wafer processing volume119.

Additionally, some wafer processes must be performed at specifictemperatures. In order to provide temperature control within the waferprocessing volume 119, thermal control devices can be disposed withinthe upper support plate 103 and the lower support plate 101. In oneembodiment, the thermal control devices can include heat exchanger fluidpathways. In another embodiment, the thermal control devices can includeelectric heating elements. In either embodiment, conduction through theupper support plate 103, the lower support plate 101, and the lowerplate 109 provide a transfer mechanism to move heat from the thermalcontrol devices to the wafer processing volume 119.

FIG. 2 is an illustration showing a close-up view of a central portionof the chamber 100 as shown in FIG. 1, in accordance with one embodimentof the present invention. The close-up view shows a verticalcross-section of half of the chamber 100, including the upper supportplate 103, the wafer processing volume 119, the wafer 117, theunderlying volume 115, the lower plate 109, the intermediate volume 113,and the lower support plate 101.

As discussed with respect to FIG. 1, the lower plate 109 serves tosupport the wafer 117 by providing the wafer support surfaces 110 uponwhich the wafer 117 will be secured during wafer processing. Each of thewafer support surfaces 110 is a part of a discrete support structure.The discrete support structures corresponding to the wafer supportsurfaces 110 are distributed in a substantially uniform mannerthroughout the underlying volume 115. Therefore, the underlying volume115 exists between the discrete support structures corresponding to thewafer support surfaces 110 and below the wafer 117. An inlet 207 isprovided for introducing fluids into the underlying volume 115. Anoutlet 205 is provided for removing fluids from the underlying volume115. In other embodiments, the inlet 207 and the outlet 205 can bedisposed at other locations within the lower plate 109. A number ofinlets/outlets 209 are also provided within the lower plate 109 tointroduce and remove fluids from the wafer processing volume 119.

As discussed with respect to FIG. 1, the lower support plate 101 servesto support the lower plate 109 by providing the support surfaces 102upon which the lower plate 109 will be secured during wafer processing.Each of the support surfaces 102 is a part of a discrete supportstructure. The discrete support structures corresponding to the supportsurfaces 102 are distributed in a substantially uniform mannerthroughout the intermediate volume 113. Therefore, the intermediatevolume 113 exists between the discrete support structures correspondingto the support surfaces 102 and below the lower plate 109. An inlet 201is provided for introducing fluids into the intermediate volume 113. Anoutlet 203 is provided for removing fluids from the intermediate volume113. In other embodiments, the inlet 201 and the outlet 203 can bedisposed at other locations within the lower support plate 101.

The wafer processing volume 119 is formed within the upper support plate103 to overlie the wafer 117 when the upper support plate 103 is joinedwith the lower support plate 101. Since the wafer 117 is nothermetically sealed to the lower plate 109 during wafer processing, thewafer processing volume 119 will be in fluid communication with theunderlying volume 115 through a limited fluid communication pathway 211at the periphery of the wafer 117. The limited fluid communicationpathway 211 is essentially the area between the wafer 117 and theperipheral wafer support surface 110 of the lower plate 109.

During operation, a pressure in the wafer processing volume 119 will bemaintained at a higher level than a pressure in the underlying volume115, thus creating a pressure differential through the wafer 117 fromtop to bottom. The pressure differential serves to push the wafer 117toward the lower plate 109 with sufficient force to secure the wafer 117to the wafer support surfaces 110. Since the pressure in the waferprocessing volume 119 is higher than the pressure in the underlyingvolume 115, some fluid will pass from the wafer processing volume 119through the limited fluid communication pathway 211 to the underlyingvolume 115. The outlet 205 can be used to remove fluid from theunderlying volume 115 as necessary.

The dimensions of the wafer processing volume 119, the underlying volume115, and the wafer support surfaces 110 can vary depending upon therequirements (e.g., pressure, fluid flow rate, fluid composition, etc. .. . ) of the wafer process to be performed. In one embodiment, aseparation distance D1 between the upper support plate 103 and the wafer117 top surface is about 0.04 inch. As used herein, the term “about”means within ±10% of a specified value. However, in other embodimentsdifferent values for D1 may be used. In one embodiment, a depth D2 ofthe underlying volume 115 between the wafer 117 and the lower plate 109can be within a range extending from about 0.005 inch to about 0.04inch. In a particular embodiment, the depth D2 is about 0.02 inch. Inone embodiment, an overlap distance D3 between the wafer 117 and theperipheral wafer support surface 110 can be within a range extendingfrom about 0.1 inch to about 0.5 inch. In a particular embodiment, theoverlap distance D3 is about 0.25 inch. The overlap distance D3 is a keyfactor in establishing the pressure drop between the wafer processingvolume 119 and the underlying volume 115, through the limited fluidcommunication pathway 211. In one embodiment, a wafer positioningtolerance D4 (i.e., nominal distance between the wafer 117 edge and awafer pocket perimeter within the lower plate 109) can be within a rangeextending from about 0.025 inch to about 0.1 inch. The wafer positioningtolerance D4 may be dictated by a precision of a robot handling device.

The wafer support surfaces 110 are configured to contact a percentage ofthe wafer 117 commensurate with the pressure differential to be appliedthrough the wafer 117. A higher pressure differential requires a higherpercentage of the wafer 117 to be in contact with the wafer supportsurfaces 110. In one embodiment, the wafer support surfaces 110 can bein contact with a percentage of the wafer 117 surface within a rangeextending from about 5% to about 80%. In another embodiment, the wafersupport surfaces 110 can be in contact with a percentage of the wafer117 surface within a range extending from about 15% to about 25%. In yetanother embodiment, the wafer support surfaces 110 can be in contactwith about 20% of the wafer 117 surface. With a differential pressurewithin a range extending from about 1 atm to about 1.5 atm, the wafersupport surfaces 110 can be in contact with a percentage of the wafer117 surface within a range extending up to about 10%. With adifferential pressure within a range extending from about 3 atm to about4 atm, the wafer support surfaces 110 can be in contact with apercentage of the wafer 117 surface within a range extending from about50% to about 70%.

It is preferable to minimize the percentage of the wafer 117 in contactwith the wafer support surfaces 110 (i.e., wafer backside contact area).Minimization of the wafer backside contact area, however, should beperformed in a manner that provides sufficient support for theparticular pressure differential to be applied between the waferprocessing volume 119 and the underlying volume 115. Minimizing thewafer backside contact area serves to reduce the potential for wafer 117contamination. Also, minimizing the wafer backside contact area reducesthe potential for particles becoming lodged between the wafer 117 andthe wafer support surfaces 110, which could cause difficulty in securingthe wafer 117.

Pressures in each of the wafer processing volume 119, the underlyingvolume 115, and the intermediate volume 113 can be controlledindependently by controlling fluid introduction to and removal from eachvolume. The lower plate 109 allows the wafer processing volume 119pressure to be adjusted relative to the intermediate volume 113pressure. In this manner, the lower plate 109 allows a high pressure tobe constrained within the wafer processing volume 119. In an alternateembodiment, the intermediate volume 113 can be over-pressurized to causea fluid to be introduced into the wafer processing volume 119 from theintermediate volume 113. Regardless, of the particular embodiment,however, the pressure differential between the two sides of the lowerplate 109 dictates the required thickness of the lower plate 109. Alarger pressure differential across the lower plate 109 requires thelower plate 109 to have a larger thickness. For the lower plate 109 tobe thinner, the pressure differential between the wafer processingvolume 119 and the intermediate volume 113 should be lower.

It is desirable to minimize the thickness of the lower plate 109 inorder to reduce the volume of outer chamber 100 material and the chamber100 overall size. However, a balance exists when determining the lowerplate 109 thickness to use and the minimum intermediate volume 113pressure to allow. A thinner lower plate 109 will reduce the overallchamber 100 size, but a lower intermediate volume 113 pressure willallow the use of a thinner lower support plate 101, by reducing apressure differential between the intermediate volume 113 and an outsideenvironment.

With an effective variation in pressure differential from the waferprocessing volume 119 to the intermediate volume 113 to the outsideenvironment, the chamber 100 size can be optimized. Thus, the use ofmultiple chamber internal volumes allows for a more compact chamber 100design. Also, minimizing the size of the wafer processing volume 119allows both the chamber size and the wafer processing cycle time to bereduced. A smaller wafer processing volume 119 requires less material toconstrain the pressure within the wafer processing volume 119.Furthermore, a smaller wafer processing volume 119 requires less time toreduce the high pressure within the wafer processing volume 119 to apressure at which the wafer 117 can be safely transferred, thus reducingthe wafer processing cycle time.

As previously mentioned, the lower plate 109 includes the number ofinlets/outlets 209 for introducing fluids to and removing fluids fromthe wafer processing volume 119. The inlets/outlets 209 are located nearthe periphery of the lower plate 109 and outside a location intended toreceive the wafer 117. The inlets/outlets 209 can be configured tocontrol a fluid flow through the wafer processing volume 119 over a topsurface of the wafer 117. It is likely that different fluid flowpatterns and pressures will work better for different wafer processingapplications. The inlets/outlets 209 in the lower plate 109 can beconfigured to provide numerous fluid flow patterns within the waferprocessing volume 119. In following, numerous lower plates 109 can bedesigned and manufactured to provide a selection of fluid flow patterns,thus allowing a suitable fluid flow pattern to be selected for aspecific wafer process. Since the lower plates 109 are interchangeable,the fluid flow pattern through the wafer processing volume 119 can bechanged without requiring other aspects of the chamber 100, beyond thelower plate 109, to be altered.

FIG. 3 is an illustration showing a top view of the lower plate 109configured to provide a linear fluid flow across the wafer 117, inaccordance with one embodiment of the present invention. The lower plate109 is defined to have a number of inlets 209B distributed in asubstantially uniform manner around a 180 degree segment of the lowerplate 109 periphery. The lower plate 109 is further defined to have anumber of outlets 209A distributed in a substantially uniform manneraround a 180 degree segment of the lower plate 109 periphery that isopposite the 180 degree segment containing the number of inlets 209B.The fluid is introduced into the wafer processing volume 119 through thenumber of inlets 209B. The fluid is removed from the wafer processingvolume 119 through the number of outlets 209A. The disposition of thenumber of inlets 209B and the number of outlets 209A causes the fluid toflow in a linear pattern across the top surface of the wafer 117 asindicated by arrows 301.

FIG. 4 is an illustration showing a top view of the lower plate 109configured to provide a conical fluid flow across the wafer 117, inaccordance with one embodiment of the present invention. The lower plate109 is defined to have a number of inlets 209B distributed in asubstantially uniform manner around a segment of the lower plate 109periphery that subtends an angle less than 180 degrees. The lower plate109 is further defined to have a number of outlets 209A distributed in asubstantially uniform manner around a segment of the lower plate 109periphery that subtends an angle less than that subtended by the numberof inlets 209B. The number of outlets 209A are positioned at a locationopposite the number of inlets 209B. The fluid is introduced into thewafer processing volume 119 through the number of inlets 209B. The fluidis removed from the wafer processing volume 119 through the number ofoutlets 209A. The disposition of the number of inlets 209B and thenumber of outlets 209A causes the fluid to flow in a conical patternacross the top surface of the wafer 117 as indicated by arrows 401. Theconical pattern can be optimized to allow the fluid flow to maintain aconstantly accelerating velocity across the top surface of the wafer117.

FIG. 5 is an illustration showing a top view of the lower plate 109configured to provide a spiral fluid flow across the wafer 117, inaccordance with one embodiment of the present invention. The lower plate109 is defined to have a number of inlets 209B distributed in asubstantially uniform manner around the lower plate 109 periphery. Thefluid is introduced into the wafer processing volume 119 through thenumber of inlets 209B. The number of inlets 209B are configured todirect the fluid in a tangential direction with respect to the wafer117. The configuration of the number of inlets 209B causes the fluid toflow in a spiral pattern across the top surface of the wafer 117 asindicated by arrows 501. In one embodiment, the fluid is removed fromthe wafer processing volume 119 through one or more outlets located inthe upper support plate 103.

FIG. 6 is an illustration showing a vertical cross-section of thechamber 100 incorporating an upper plate 601, in accordance with oneembodiment of the present invention. The chamber 100 incorporates thelower plate 109, the lower support plate 101, the bolts 111, the bolts105, and the seal 107 as previously described with respect to FIG. 1.The chamber 100 embodiment illustrated in FIG. 6, however, incorporatesa different upper support plate 103A.

The upper support plate 103A is configured to interface with the topsection of the lower support plate 101. The upper support plate 103Aincludes a number of support surfaces 602. The support surfaces 602 aredistributed within an intermediate volume 605 defined within a bottomportion of the upper support plate 103A. The support surfaces 602 arecapable of supporting the upper plate 601 at discrete locations in asubstantially uniform manner. The number and location of the supportsurfaces 602 depends on a pressure differential between the two sides ofthe upper plate 601. The upper plate 601 can be secured to the uppersupport plate 103A by a number of bolts 603. When secured to the uppersupport plate 103A, the upper plate 601 serves as a lower boundary tothe intermediate volume 605.

The upper support plate 103A further includes the wafer processingvolume 119. The wafer processing volume 119 is configured to overlie thewafer 117 when the upper support plate 103A is attached to the lowersupport plate 101. The wafer processing volume 119 is also configured tounderlie the upper plate 601 when the upper plate 601 is secured to theupper support plate 103A. In this manner, the upper plate 601 serves asan upper boundary to the wafer processing volume 119.

FIG. 7 is an illustration showing a close-up view of a central portionof the chamber 100 as shown in FIG. 6, in accordance with one embodimentof the present invention. The close-up view shows a verticalcross-section of half of the chamber 100, including the upper supportplate 103A, the upper plate 601, the intermediate volume 605, the waferprocessing volume 119, the wafer 117, the underlying volume 115, thelower plate 109, the intermediate volume 113, and the lower supportplate 101.

The lower plate 109, having the wafer support surfaces 110 distributedwithin the underlying volume 115 and containing the inlet 207, theoutlet 205 and the inlet/outlet 209, is the same as previously describedwith respect to FIG. 2. Also, the lower support plate 101, having thesupport surfaces 102 distributed within the intermediate volume 113 andcontaining the inlet 201 and the outlet 203, is the same as previouslydescribed with respect to FIG. 2.

As discussed with respect to FIG. 6, the upper support plate 103A servesto support the upper plate 601 by providing the support surfaces 602upon which the upper plate 601 will be secured during wafer processing.Each of the support surfaces 602 is a part of a discrete supportstructure. The discrete support structures corresponding to the supportsurfaces 602 are distributed in a substantially uniform mannerthroughout the intermediate volume 605. Therefore, the intermediatevolume 605 exists between the discrete support structures correspondingto the support surfaces 602 and above the upper plate 601. An inlet 701is provided for introducing fluids into the intermediate volume 605. Anoutlet 703 is provided for removing fluids from the intermediate volume605. In other embodiments, the inlet 701 and the outlet 703 can bedisposed at other locations within the upper support plate 103A.

Pressures in each of the wafer processing volume 119 and theintermediate volume 605 can be controlled independently by controllingfluid introduction to and removal from each volume. The upper plate 601allows the wafer processing volume 119 pressure to be adjusted relativeto the intermediate volume 605 pressure. In this manner, the upper plate601 allows a high pressure to be constrained within the wafer processingvolume 119. In an alternate embodiment, the intermediate volume 605 canbe over-pressurized to cause a fluid to be introduced into the waferprocessing volume 119 from the intermediate volume 605. Regardless, ofthe particular embodiment, however, the pressure differential betweenthe two sides of the upper plate 601 dictates the required thickness ofthe upper plate 601. A larger pressure differential across the upperplate 601 requires the upper plate 601 to have a larger thickness. Forthe upper plate 601 to be thinner, the pressure differential between thewafer processing volume 119 and the intermediate volume 605 should belower.

It is desirable to minimize the thickness of the upper plate 601 inorder to reduce the volume of outer chamber 100 material and the chamber100 overall size. However, a balance exists when determining the upperplate 601 thickness to use and the minimum intermediate volume 605pressure to allow. A thinner upper plate 601 will reduce the overallchamber 100 size, but a lower intermediate volume 605 pressure willallow the use of a thinner upper support plate 103A, by reducing apressure differential between the intermediate volume 605 and an outsideenvironment. With an effective variation in pressure differential fromthe wafer processing volume 119 to the intermediate volume 605 to theoutside environment, the chamber 100 size can be optimized.

The upper plate 601 includes a number of inlets/outlets 705 forintroducing fluid to and removing fluid from the wafer processing volume119, as indicated by arrows 707. The inlets/outlets 705 are distributedacross the upper plate 601 and are configured to control the fluid flowthrough the wafer processing volume 119 over the top surface of thewafer 117. As previously mentioned, it is likely that different fluidflow patterns and pressures will work better for different waferprocessing applications. The inlets/outlets 705 in the upper plate 601can be configured to provide numerous fluid flow patterns within thewafer processing volume 119. Additionally, the inlets/outlets 705 in theupper plate 601 can be configured to work in conjunction with theinlets/outlets 209 in the lower plate 109 to provide fluid flow patternswithin the wafer processing volume 119. In following, numerous upperplates 601 can be designed and manufactured to provide a selection offluid flow patterns, thus allowing a suitable fluid flow pattern to beselected for a specific wafer process. As with the lower plates 109, theinterchangeability of the upper plates 601 allows the fluid flow patternthrough the wafer processing volume 119 to be changed without requiringother aspects of the chamber 100 to be changed.

FIG. 8A is an illustration showing an upper plate 601A configured toprovide a central fluid feed and a peripheral fluid exhaust, inaccordance with one embodiment of the present invention. The upper plate601A includes a number of inlets 705A distributed in a location near acenter of the upper plate 601A. In one embodiment, the upper plate 601Aincludes a number of outlets 705B distributed about periphery of theupper plate 601A at a location near the periphery of the wafer 117. Inanother embodiment, the lower plate 109 includes a number of outlets209A distributed in a substantially uniform manner around the peripheryof the lower plate 109. In yet another embodiment, the upper plate 601Aincludes the number of outlets 705B and the lower plate 109 includes thenumber of outlets 209A. In either embodiment, the fluid is introducedinto the wafer processing volume 119 through the number of inlets 705Aand removed from the wafer processing volume 119 through the number ofoutlets 705B and/or 209A. The configuration of the number of inlets 705Aand the number of outlets 705B and/or 209A causes the fluid to flow froma central region to a peripheral region of the wafer 117.

FIG. 8B is an illustration showing the use of fluid channels within theupper plate 601A, in accordance with one embodiment of the presentinvention. Fluid channels 801 are provided for transferring fluid to thenumber of inlets 705A. Fluid channels 803 are provided for transferringfluid from the number of outlets 705B. Use of fluid channels toindependently control different inlets and outlets within the upperplate 601A allows for pressure equalization and flow pattern controlwithin the wafer processing volume 119. Additionally, the use of fluidchannels provides flexibility in changing flow patterns within the waferprocessing volume 119 and in varying the pressure differential betweenthe wafer processing volume 119 and the intermediate volume 605.

FIG. 9 is an illustration showing an upper plate 601B configured toprovide a peripheral fluid feed and a central fluid exhaust, inaccordance with one embodiment of the present invention. The upper plate601B includes a number of outlets 705C distributed in a location near acenter of the upper plate 601B. In one embodiment, the upper plate 601Bincludes a number of inlets 705D distributed about periphery of theupper plate 601B at a location near the periphery of the wafer 117. Inanother embodiment, the lower plate 109 includes a number of inlets 209Bdistributed in a substantially uniform manner around the periphery ofthe lower plate 109. In yet another embodiment, the upper plate 601Bincludes the number of inlets 705D and the lower plate 109 includes thenumber of inlets 209B. In either embodiment, the fluid is introducedinto the wafer processing volume 119 through the number of inlets 705Dand/or 209B and removed from the wafer processing volume 119 through thenumber of outlets 705C. The configuration of the number of inlets 705Dand/or 209B and the number of outlets 705C causes the fluid to flow froma peripheral region to a central region of the wafer 117.

FIG. 10 is an illustration showing an exemplary distribution of theinlets/outlets 705 across the upper plate 601, in accordance with oneembodiment of the present invention. The number and distribution ofinlets/outlets 705 will depend upon the desired fluid flow pattern to beapplied within the wafer processing volume 119. The distribution ofinlets/outlets 705 as shown in FIG. 10 provides an example of possibleinlet/outlet 705 locations across the upper plate 601. Otherinlet/outlet 705 numbers and distributions can be employed to satisfythe fluid flow pattern requirements of a particular wafer processingoperation.

FIG. 11 is an illustration showing a flowchart of a method for making awafer processing chamber, in accordance with one embodiment of thepresent invention. The method includes an operation 1101 in which alower support plate is formed. In one embodiment, the lower supportplate is formed from stainless steel. In other embodiments, the lowersupport plate can be formed from other materials that are compatiblewith the processes to be performed within the wafer processing chamber.The forming can be accomplished by pouring molten material into a moldor by machining a block of material. The lower support plate is formedto have support surfaces distributed within a first volume definedwithin the lower support plate. The first volume is defined to have afirst fluid inlet and a first fluid outlet. The lower support plate iscapable of withstanding a pressure differential to be applied betweenvolumes located at each side of the lower support plate.

The method also includes an operation 1103 in which a wafer supportplate is formed. In one embodiment, the wafer support plate is formedfrom stainless steel. In other embodiments, the wafer support plate canbe formed from other materials that are compatible with the processes tobe performed within the wafer processing chamber. The forming can beaccomplished by pouring molten material into a mold or by machining ablock of material. The wafer support plate is formed to have wafersupport surfaces distributed within a second volume defined within thewafer support plate. The wafer support surfaces are configured toreceive a wafer. Once received, the wafer forms an upper boundary forthe second volume defined within the wafer support plate. The secondvolume is defined to have a second fluid inlet and a second fluidoutlet. Additionally, fluid inlets and fluid outlets are provided at aperiphery of the wafer support plate and outside a location that is toreceive the wafer. The peripheral fluid inlets and fluid outlets of thewafer support plate can be configured to create a fluid flow patternwithin the third volume. In some embodiments, the fluid flow pattern canbe either a linear pattern, a conical pattern, or a spiral pattern. Inother embodiments, different fluid flow patterns can be created tosatisfy the requirements of a wafer processing operation. The wafersupport plate is capable of withstanding a pressure differential to beapplied between volumes located at each side of the wafer support plate.

The method further includes an operation 1105 in which the wafer supportplate is secured to the lower support plate. Once secured, the wafersupport plate is supported by the support surfaces distributed withinthe first volume of the lower support plate. Also, the wafer supportplate serves as an upper boundary for the first volume defined withinthe lower support plate.

The method continues with an operation 1107 in which an upper supportplate is formed. In one embodiment, the upper support plate is formedfrom stainless steel. In other embodiments, the upper support plate canbe formed from other materials that are compatible with the processes tobe performed within the wafer processing chamber. The forming can beaccomplished by pouring molten material into a mold or by machining ablock of material. The upper support plate is formed to contain a thirdvolume that is configured to overlie the wafer to be received by thewafer support surfaces of the wafer support plate. The upper supportplate is capable of withstanding a pressure differential to be appliedbetween volumes located at each side of the upper support plate.

In one embodiment, support surfaces are formed within the upper supportplate. The support surfaces are distributed within a fourth volume. Thefourth volume can have a fluid inlet and a fluid outlet. The supportsurfaces formed within the upper support plate are configured to receiveand support an upper plate. In accordance with this embodiment, themethod includes an optional operation 1109, in which the upper plate isformed. In one embodiment, the upper plate is formed from stainlesssteel. In other embodiments, the upper plate can be formed from othermaterials that are compatible with the processes to be performed withinthe wafer processing chamber. The forming can be accomplished by pouringmolten material into a mold or by machining a block of material. Theupper plate is formed to have fluid inlets and fluid outlets capable ofintroducing fluid to and removing fluid from third volume. The fluidinlets and fluid outlets of the upper plate can be configured to createa fluid flow pattern within the third volume. In some embodiments, thefluid flow pattern can be either a linear pattern, a conical pattern, aspiral pattern, a center feed with peripheral exhaust pattern, or aperipheral feed with center exhaust pattern. In other embodiments,different fluid flow patterns can be created to satisfy the requirementsof a wafer processing operation. Also in accordance with thisembodiment, the method includes an optional operation 1111, in which theupper plate is secured to the support surfaces of the upper supportplate. In this manner, the upper plate serves as a lower boundary to thefourth volume and an upper boundary to the third volume. The upper plateis capable of withstanding a pressure differential between the fourthvolume and the third volume.

The method also includes an operation 1113 in which the upper supportplate is secured to the lower support plate. Securing the upper supportplate to the lower support plate causes the third volume defined withinthe upper support plate to be isolated from an outside environment.Isolation of the third volume from the outside environment is enabled bya seal disposed between the upper support plate and the lower supportplate.

FIG. 12 is an illustration showing a flowchart of a method forperforming a wafer cleaning process, in accordance with one embodimentof the present invention. The method includes an operation 1201 forproviding a chamber in which the wafer cleaning process can beperformed. The chamber includes a first volume configured to overlie awafer to be cleaned. The chamber also includes a plate configured tosupport the wafer. A second volume is defined within the plate directlybelow the wafer. Also in the chamber, a support structure is provided tosupport the plate. The support structure includes a third volume locateddirectly below the plate. The method further includes an operation 1203for pressurizing the first volume to have a higher pressure than thesecond volume. Also in the method, an operation 1205 is provided forpressurizing the second volume to have a higher pressure than the thirdvolume. The third volume is pressurized to have a pressure between thatof the second volume and an environment outside the chamber. The methodalso includes an operation 1207 for providing a fluid to the firstvolume that overlies the wafer to be cleaned. The fluid is formulated toeffect the wafer cleaning process. In one embodiment, the fluid is asupercritical fluid.

The wafer processing chamber of the present invention is well suited foruse in a wafer process that utilizes a supercritical fluid. Aspreviously described, the wafer processing chamber is suited forcontrolling the pressure within the wafer processing volume.Additionally, the wafer processing chamber is capable of controlling thepressure differentials that exist between the wafer processing volume,the intermediate volume of the chamber, and the outside environment.Having an ability to adjust the wafer processing volume pressurerelative to the chamber intermediate volume pressures, as afforded bythe present invention, can be valuable in designing a supercriticalfluid processing chamber that is minimal in size. Also, in supercriticalfluid wafer processing, the pressure within the wafer processing volumemust be controlled to maintain the supercritical state of the fluid.

FIG. 13 is an illustration showing a generalized material phase diagram.The phase of the material is represented as regions of solid, liquid,and gas, wherein the presence of a particular phase is dependent onpressure and temperature. The gas-liquid phase boundary follows anincrease in both pressure and temperature up to a point called thecritical point. The critical point is delineated by a critical pressure(P_(c)) and a critical temperature (T_(c)). At pressures andtemperatures beyond P_(c) and T_(c), the material becomes asupercritical fluid.

Wafer cleaning operations can be performed using the supercriticalfluid. The supercritical fluid shares the properties of both a gas phaseand a liquid phase. The supercritical fluid has near zero surfacetension. Therefore, the supercritical fluid can reach into and betweensmall features on the wafer surface. Also, the supercritical fluid has adiffusivity property similar to a gas. Therefore, the supercriticalfluid can get into porous regions of wafer materials, such as low-Kdielectric material, without becoming trapped. Additionally, thesupercritical fluid has a density similar to a liquid. Therefore, moresupercritical fluid can be transported to the wafer in a given amount oftime as compared to a gas.

Wafer processing with the supercritical fluid must be performed at highpressures to maintain the supercritical state of the fluid. For example,supercritical fluid processing can be performed at pressures rangingfrom about 68 atm to about 273 atm. Therefore, the wafer processingchamber must be able to withstand the associated high pressures. Thewafer processing chamber of the present invention is capable ofwithstanding and controlling the high pressures associated withsupercritical fluids.

Generally speaking, in supercritical fluid processes, the waferprocessing volume is pressurized and the temperature within the waferprocessing volume is controlled. The wafer processing volume pressureand temperature are controlled to maintain a supercritical fluid state.In an exemplary embodiment, the wafer processing volume can bepre-pressurized with CO₂ only or with a mixture of CO₂ and anappropriate chemistry. The critical pressure and temperature for CO₂ isapproximately 73 atm and 31° C., respectively. It should be noted thatthe supercritical fluid used in combination with the wafer processingchamber of the present invention is not restricted to CO₂. Othersuitable supercritical fluids can also be used. Additionally, thechemistry of the supercritical fluid may include additives such asco-solvents, co-chelating agents, surfactants, or any combinationthereof. The additives contained within the supercritical fluid can beuseful for performing specific functions, such as dissolving andremoving photoresist, dissolving and removing organic residue, andchelating metals, among others.

The advantages of the wafer processing chamber of the present inventionare numerous. One advantage is that the wafer processing chamber iscompletely configurable. By interchanging the upper and lower plates,the chamber can be converted to several different configurations withoutchanging the main chamber body. This advantage allows one type ofchamber to be used for several potential wafer processing applications.Also, the interchangeability of the upper and lower plates allows thewafer processing volume pressure and flow pattern to be appropriatelyselected for a particular wafer processing application. Additionally,during a wafer cleaning process, there is a potential that materialbeing cleaned from the wafer can become trapped in cavities within thechamber. Since the upper and lower plates are removable, both thechamber and the upper and lower plates can be more easily cleaned.

The wafer processing chamber of the present invention can beincorporated into a wafer processing cluster architecture. In oneexample, the wafer processing cluster architecture can incorporateseparate modules for performing wafer cleaning operations, wafer etchingoperations, CMP operations, and wafer rinsing operations. Additionally,in the wafer processing cluster architecture, the wafer can betransferred between different modules using a robotic wafer handlingmechanism or a track mechanism.

While this invention has been described in terms of several embodiments,it will be appreciated that those skilled in the art upon reading thepreceding specifications and studying the drawings will realize variousalterations, additions, permutations and equivalents thereof. It istherefore intended that the present invention includes all suchalterations, additions, permutations, and equivalents as fall within thetrue spirit and scope of the invention.

1. A method for performing a wafer cleaning process, comprising:providing a chamber, including, a first volume configured to overlie awafer; a plate configured to support a wafer, the plate furtherconfigured to define a second volume directly below the wafer when thewafer is supported on the plate, the plate including fluid inlets andfluid outlets defined in a periphery of the plate and outside a portionof the plate defined to support the wafer, the fluid inlets and fluidoutlets oriented to direct a fluid flow through the first volume in aset pattern; a support structure configured to support the plate, thesupport structure further configured to define a third volume directlybelow the plate; placing a wafer on the portion of the plate defined tosupport the wafer; pressurizing the first volume, the second volume, andthe third volume, the pressurizing causing the first volume to have ahigher pressure than the second volume, the pressurizing further causingthe second volume to have a higher pressure than the third volume; andproviding a fluid to the first volume through the fluid inlets andremoving the fluid from the first volume through the fluid outlets suchthat the fluid flows through the first volume in the set pattern, thefluid being formulated to effect a wafer cleaning process.
 2. A methodfor performing a wafer cleaning process as recited in claim 1, whereinthe fluid is a supercritical fluid.
 3. A method for performing a wafercleaning process as recited in claim 1, wherein the chamber is providedas part of a wafer processing cluster architecture.
 4. A method forperforming a wafer cleaning process as recited in claim 1, furthercomprising: allowing the fluid to move from the first volume to thesecond volume, and from the second volume to the third volume.
 5. Amethod for performing a wafer cleaning process as recited in claim 1,wherein a higher pressure of the first volume relative to a pressure ofthe second volume serves to hold the wafer on the plate.
 6. A method forperforming a wafer cleaning process as recited in claim 1, furthercomprising: controlling a pressure differential between the secondvolume and the third volume within a ranges extending from about 1 atmto about 4 atm.
 7. A method for performing a wafer cleaning process asrecited in claim 1, wherein the set pattern of the fluid flow throughthe first volume is one of a linear flow pattern, a conical flowpattern, and a spiral flow pattern.
 8. A method for performing a wafercleaning process as recited in claim 1, wherein the plate includes anumber of support surfaces upon which the wafer is supported, andwherein the second volume exists between the number of support surfacesof the plate and below the wafer when the wafer is supported on theplate.
 9. A method for performing a wafer cleaning process as recited inclaim 8, wherein the number of support surfaces are distributed in asubstantially uniform manner across the portion of the plate defined tosupport the wafer.
 10. A method for performing a wafer cleaning processas recited in claim 1, wherein the chamber includes an upper structurehaving a cavity defined therein, the method including an operation forsecuring the upper structure to the support structure such that theupper structure interfaces with the support structure outside aperiphery of the plate, and such that the cavity within the upperstructure defines the first volume.
 11. A method for performing a wafercleaning process as recited in claim 10, wherein the upper structure issecured to the support structure so as to form a seal at the interfacebetween the upper structure and the support structure, wherein the sealserves to isolate the first volume from an environment outside of thechamber.
 12. A method for cleaning a wafer, comprising: placing a waferon a support plate, the support plate including a number of fluid inletsand a number of fluid outlets defined in a periphery of the supportplate, the periphery of the support plate defined outside an area of thesupport plate on which the wafer is placed; and flowing a cleaning fluidover the wafer from the number of fluid inlets to the number of fluidoutlets in a set fluid flow pattern, wherein the set fluid flow patternis defined by positions and orientations of the number of fluid inletsand the number of fluid outlets.
 13. A method for cleaning a wafer asrecited in claim 12, further comprising: enclosing a volume over boththe wafer and the support plate in a sealed manner; and controlling apressure within the volume.
 14. A method for cleaning a wafer as recitedin claim 13, wherein the cleaning fluid is a supercritical fluid, andwherein the pressure within the volume is controlled to maintain thecleaning fluid in a supercritical state.
 15. A method for cleaning awafer as recited in claim 12, wherein the set fluid flow pattern is oneof a linear flow pattern, a conical flow pattern, and a spiral flowpattern.